The present invention relates to the field of digital imaging. Specifically, the present invention relates to an apparatus for capturing images and barcodes having one or more lenses providing a variable-focal-length region for barcodes and a fixed-focal-length region for images.
Barcodes have become a ubiquitous way of coding information in a machine-readable form because of the ease with which barcodes may be scanned, processed, stored, etc. via an electronic device. This allows for an accurate and rapid process. However, factors such as cost, power consumption, size, weight, accuracy, ease of use, location of scanner relative to barcode, etc. limit the applications for which conventional barcode scanners are suitable.
One problem with reading barcodes is that the image of the barcode must be sufficiently focused on a sensing component in order to accurately decipher the barcode pattern. The best-known conventional way of reading barcodes is with laser scanners, which have become standard at department and grocery stores. Such devices operate by emitting a beam of laser light, which strikes the surface of the object on which the barcode is imprinted and is then reflected back to the scanning device. Because laser beam is coherent, laser scanners do not face a focusing problem. However, laser scanners are mechanically complex and consequently are relatively expensive and heavy. Also, mechanical devices tend to break down much faster than, for example, a device with no moving mechanical parts.
In order to properly read a barcode, a laser scanner typically has at least one rotating mirror and perhaps several fixed mirrors, upon which a laser beam is reflected before leaving the scanner. The laser scanner may emit multiple such beams as the mirror(s) rotate. In this fashion, the scanner may trace laser beam lines having various angles with respect to one another on the surface containing the barcode. Because the lines will be at various angles with respect to one another, it is likely that at least one line will trace across the entire barcode, thus allowing the barcode to be read. The beams then reflect off the surface containing the barcode and return to the scanner where signal processing interprets the barcode.
Unfortunately, such laser scanners use considerable power. First, considerable power is needed for the laser, and second, considerable power is needed for the motor to rotate the mirror(s). While power consumption may not be a severe issue in a retail store application, power consumption is of great concern if the scanning device is to be used in the field. For example, it is desirable to allow a user without access to an electrical outlet to scan barcodes.
Two further problems with such laser scanners are their size and weight. The motors, mirrors, lasers, etc. just described make the scanner heavy and bulky. However, a relatively lightweight and compact solution is desired for a user in the field.
Another type of barcode reader emits a single incoherent point light source, usually infra-red, and detects its reflection without using rotating mirrors. A single light source is emitted from the barcode reader, reflected off the object with the barcode, and read by a single detector that is generally nearby the light source. While these readers do not require rotating mirrors, the barcode reader must be swiped across the barcode manually to obtain an accurate reading. For example, the barcode reader must be physically touching the object with the barcode or at least be within a few millimeters for the light to reflect back properly for an accurate reading. This leads to error prone measurements, barcode reader wear, and slow operating speed.
It has also been suggested that a digital camera be used to read barcodes. However, instead of using laser light, digital cameras generally use visual or infrared light. As such, focusing the image of the barcode on the sensing array of the camera is very problematic. Consequently, this requires that the barcode always be the same distance from the camera to ensure the barcode is in focus on the sensing array. A conventional solution requires the scanning device to touch the barcode or be a fixed distance away, often no more than a few millimeters.
Conventional digital cameras generally use a charge-coupled device (CCD) array to capture images. Each axis of the array may comprise anywhere from a few hundred to a few thousand pixels. Problematically, those arrays comprising a few thousand pixels per axis are expensive and those comprising only a few hundred pixels per axis do not have sufficient resolution for applications such as reading barcodes. Hence, CCD based barcode readers face a cost versus accuracy tradeoff.
Thus, one problem with conventional barcode scanning devices is they consume too much power, and thus may be unsuitable for a battery operated device. Another problem with conventional devices is that they have too many moving mechanical parts and are thus too unreliable. Another problem with conventional devices is that they are heavy and bulky. Another problem with some conventional devices is that they require the scanner to be placed either very close to or touching the object with the barcode. Additionally, CCD based barcode readers face a cost versus accuracy tradeoff.
The present invention pertains to an apparatus for capturing images and barcodes. The apparatus has an image-sensing device and a lens having a variable-focal-length region and a substantially fixed-focal-length region. The variable-focal-length region focuses light onto a first region of the image-sensing device and the substantially fixed-focal-length region focuses light onto a second region of the image-sensing device. The variable-focal-length region varies such that different portions of that region of the lens focus objects at different distances from the lens in different areas of the first region of the image-sensing device. Thus, the device is able to focus, in the first region of the image-sensing device, objects at varying distances from the apparatus.